1. Field of the Invention
The present invention includes a chemical weapons (CW) agent decontaminating system comprising absorptive particles and a solution that will effectively degrade chemical warfare agents. The solution can be any decontamination solution that is compatible with the absorptive particles.
The decontamination system described in detail in this invention is an environmentally safe decontamination system for CW agents, such as nerve agents (G and V-type agents) and mustard agent (HD). The decontamination system can be applied to a surface which is contaminated by a CW agent.
2. Brief Description of the Related Art
Chemical weapons are a possible threat if used by terrorists or military organizations against civilian populations or military targets. In the event of such an attack, it will be necessary to have an environmentally safe chemical system to clean up the affected area by decontaminating CW agents into less hazardous chemicals.
Several types of toxic chemical compounds are known. These include mustard (HD) and nerve agents. Mustard agents or gases, also called blister agents, may be nitrogen or chlorinated sulfur compounds. The most common type of mustard agents are the chlorinated sulfur compounds. Long after mustard gas was discovered in 1822, it was used in World War I as a CW agent, causing approximately 400,000 casualties. The sulfur mustard gas is chemical known as bis-(chloroethyl)-sulphide. The nitrogen mustard gas is chemically known as tris(2-chloroethyl)-amine. Mustard gas is a colorless, oily liquid having a garlic or horse-radish odor. It is slightly soluble in water, complicating removal by washing. It primarily attacks humans through inhalation and dermal contact, having an Airborne Exposure Limit (AEL) of 0.003 mg/m3. Mustard gas is a vesicant and a alkylating agent which produces a cytotoxic reaction to the hematopoietic tissues. Symptoms usually take effect 4 to 24 hours after initial contact. The rate of detoxification of mustard gas is slow and repeated exposure yields a cumulative effect.
Nerve agents or gases were discovered in 1936, during research on more effective pesticides. Nerve agents inhibit a certain enzyme within the human body from destroying a substance called acetylcholine. This produces a nerve signal within the body forcing the muscles to contract. Nerve agents have an Airborne Exposure Limit (AEL) of 0.00001 mg/m3.
Currently, one of the primary chemical warfare agent decontaminating solutions is Decontamination Solution 2. Decontamination Solution 2, or DS2, is a chemical warfare decontaminating solution used by the United States Army. DS2 contains approximately 70% diethylenetriamine (DETA), 28% ethylene glycol monomethyl ether (EGME), and 2% NaOH by weight, and is used for decontaminating a variety of chemical warfare agents. However, DS2 is toxic, corrosive, flammable and hazardous to the environment. EGME is teratogenic, and the secondary amine structure in DETA possesses a possible health hazard from conversion to a potential N-nitrosoamine carcinogen. In addition, DS2 is extremely resistant to biodegradation, particularly with regard to the DETA component of the solution.
Another common chemical decontamination system is STB/HTB slurry. As with DS2 this chemical decontamination system is hazardous to the environment, very corrosive, and can destroy or damage most materials, including plastic and rubber materials, various metals, and delicate electronic equipment. Also, handling these decontamination solutions requires protective gear which results in a cumbersome operation. With STB, the clean up after the application has to be done either by mechanically removing the upper layer of the contaminated surface or by use of concentrated acids to dissolve this layer.
In the last two decades, efforts have been made to formulate new decontamination systems to replace these current decontamination means. To overcome the problems, liquid decontamination systems based on hydrogen peroxide solutions were developed that have the potential to be effective at decontaminating chemical warfare (CW) materials, as well as having a reduced environmental impact compared to previously available systems. The hydrogen peroxide based decontamination solution is described in U.S. Pat. No. 6,245,958, the entire disclosure of which is herein incorporated by reference. The hydrogen peroxide decontamination solution has a broad-spectrum reactivity toward CW agents, while achieving a significant reduction in the toxic, corrosive and environmentally harmful nature of the decontaminant. However, as a liquid the application of the hydrogen peroxide decontamination solution to a surface is problematic because it flows, does not form a surface barrier, and contact time with the contaminated surface is sometimes not sufficient to decontaminate the surface.
Sorbents can be used to absorb CW agent contamination. Examples of these sorbents are described in U.S. Pat. Nos. 5,689,038 and 6,852,903, the entire disclosure of which is herein incorporated by reference.
Usually, the absorption process is fast and the agent is held inside the sorbents, thus reducing its hazard by decreasing its vapor pressure. Use of these sorbents thus makes decontamination methods possible. For example, one method of decontaminating a surface that is believed to include a toxic agent involves coating the contaminated surface with a reactive sorbent, and to decontaminate the absorbed contaminant. The main disadvantage of this approach is that the contaminated sorbent particles have to be decontaminated. The sorbent materials have large surface areas, are very porous, and may be light enough to be airborne, with the result that the hazard can be spread instead of being confined.
Thus, there still exists a need for a decontamination system wherein the decontaminating agent is non-toxic, non-corrosive, non-flammable can be biodegraded or otherwise less hazardous to the environment then current decontamination systems.